It might sound silly to call a water bottle an accessory, but as cute as water bottles come these days, they're kind of a fashion statement. Unless you're going on a vacation where you know the water isn't safe and must drink bottled H2O, consider bringing along your own water bottle.
For one thing, carrying your own water bottle is eco-friendly and cheaper than buying lots of waters and sodas. You can fill up a reusable bottle yourself at your hotel or beach house with whatever you want -- water, iced tea or juice. Some cafes will even give you free refills, so ask them to fill up your bottle. You can buy BPA-free stainless steel bottles just about anywhere, and they come in a great variety of designs and colors.
Look for bottles that have clips so you can attach them to your bag or backpack, too. And don't forget that you can also fill up your bottle with your morning coffee.